1. Field of the Invention
The present invention relates to a key input device equipped with an input key for a pushbutton switch for the input operation of an electronic apparatus, e.g., a portable information terminal, such as a mobile telephone or PDA, an AV apparatus, a car navigation system, and a remote controller for various apparatuses.
2. Description of the Related Art
An electronic apparatus is equipped with a number of input keys for executing the functions thereof. Recently, with the advent of multifunction apparatuses, it has now become quite a common practice to provide an apparatus with a key input device in which a single input key is used for a number of different input purposes.
As an example of an apparatus equipped with such a key input device, FIG. 14 shows a mobile telephone 1. This mobile telephone 1 is equipped with an input key group 2 with numerals, symbols, patterns, etc. Above the input key group 2, there is provided an input key 3 of an elliptical flat configuration having upper, lower, right, and left triangular symbols. This input key 3 is generally called a multi-point input key or a multi-directional input key and has a pressurizing operation surface 4 with triangular symbols 4a. By appropriately depressing one of these triangular symbols 4a of the pressurizing operation surface 4, it is possible to select from items displayed on a display screen 5, and to move a cursor on the display screen 5 up and down and to the right and left. Of course, under the input key 3 making these operations possible, there are provided, under the triangular symbols 4a, a printed circuit board (not shown) and contact portions thereof. When one of the triangular symbols 4a is depressed, the input key 3 oscillates so as to be tilted (sink) by a predetermined amount to bring the contact portion of the printed circuit board into conduction, whereby the circuit board is closed to realize the operations as described above.
This input key 3 enabling multiple operations as described above, which advantageously allows an apparatus incorporating it to meet the mutually contradictory requirements of multifunctionality and space saving, is widely used not only in the mobile telephone 1 as shown but also in various apparatuses. However, in actuality, it does not always provide satisfactory results in terms of operability.
For example, in the above-described input key 3, as long as each triangular symbol 4a is correctly depressed, it is possible to bring the corresponding contact portion of the printed circuit board into conduction. However, if it is depressed at an erroneous operating point deviated therefrom, the contact portions corresponding to adjacent, other triangular symbols 4a will also be brought into conduction. Such duplex input will necessitate re-input or lead to malfunction of the mobile telephone 1.
This problem in operability is experienced not only with the input key 3 called a multi-point input key having a plurality of operating points (triangular symbols 4a), but also with an input key called a seesaw key having only two operating points on a rectangular or elliptical depressing operation surface and an input key called a mono-directional key having only one operating point on a rectangular or elliptical depressing operation surface. That is, there are cases where the contact portion of the printed circuit board is not brought into conduction even when the operator believes that he has depressed the operating point.